Questions tagged [radio-frequency]

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Surface Roughness of a material in CST

I am adding an aluminium with a rough surface in CST Studio, but there is only thickness input (how thick the rough surface is), but as per ISO standards they are different types of rough surface with ...
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Ferrite material in CST Studio

I want to add a ferrite material in CST Studio for shielding effectiveness simulations, but not able to find any dispersion data for the material. I want to add a ferrite material in CST Studio for ...
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30 views

Will a sheet of carbon atoms reflect radio waves?

I am working out some details in a SciFi novel. I'm thinking of having spec ops who would use a device that could manipulate carbon atoms to form and maintain large, rigid, one-atom thick carbon ...
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1answer
25 views

How I simulate this in CST Studio? [closed]

I am trying to simulate this coaxial transmission line setup for EMI shielding. Placed the Aluminium sample as seen below (in the middle). I am new on this software, learned simulating the coaxial ...
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27 views

Intuitive explanation of Nyquist rate?

Is there an intuitive way to understand Nyquist rate (i.e., that, in order to prevent loss, an analog signal must be digitized at a rate twice as high as the highest frequency component of the signal)....
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How to calculate resolution given sampling rate/size?

In a research paper documenting the analog to digital conversion process of an experiment’s radio receiver, the following is written: The station consists of 10 channels. Each channel writes 1 ...
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Inferring angle of source?

Given the relative distance of 3 radio antennae, I want to infer an incident angle for some radio source seen by all 3 antennae, which I know to be on the ground. All I know is the relative locations ...
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25 views

What is a “strong line”?

What is a “strong line” in an FFT (Fourier Transform) waveform? How does one identify a “strong line” in an FFT trace?
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1answer
37 views

What does it take to build an effective Faraday cage at bedroom-scale? [closed]

I want to block all EMF transmissions -- tv, radio, cell phone, wifi etcetera. I'm not trying to protect myself from an atmospheric detonation or solar storms, just the RF / EM "noise" of ...
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Monotonicity of sum of two Fresnel Integrals

This question is cross posted on Math Stack Exchange https://math.stackexchange.com/questions/3747009/monotonicity-of-sum-of-two-fresnel-integrals I am studying single-knife edge diffraction of radio ...
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1answer
61 views

Why is the transmission data rate between Mars and Earth so low?

I read that we get between 500 and 32k bits per second when sending data from Mars to Earth. Apparently it's substantially higher between Moon and Earth. What are the reasons? Please explain the ...
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What is “spectral turnover”?

In a paper which deals with the spectra of radio frequency cosmic events, the word “spectral turnover” is used. What is “spectral turnover”?
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Estimation of power of received radio signal

I would like to estimate the magnitude of a radio signal received from a transmitter by first principles: Transmitter antenna length $L=1$ m Transmitter antenna cross-sectional area $A=1\hbox{ cm}^2$ ...
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How can I calculate “temporal parallax”?

A radio transient was observed by an observatory. I know the observatory’s location, the pointing center of the beam in galactic coordinates and right ascension/declination, and the exact time the ...
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What is the “single pulse radiometer equation”?

This document https://arxiv.org/pdf/1601.03547.pdf refers to the “single pulse radiometer equation”. Apparently, it’s used to calculate the flux of radio transients. What is the “single pulse ...
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23 views

Is there a way to measure flux indirectly?

Is it possible to calculate the flux of some electromagnetic radiation (say, a radio wave) using other parameters?
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Do the free electrons causing the dispersion in the 'Dispersion Measure' of an FRB refract or re-emit the long-wavelength RF waves?

If the free electrons in the interstellar and intergalactic medium absorb then elastically re-emit the longer-wavelength radio waves coming from an FRB, that would reduce their power, because they are ...
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26 views

Why are low-frequency radio transients so rare?

Why are low-frequency radio transient (fast radio bursts, etc) so rare? Is it due to our observational equipment, or something intrinsic to transient phenomena?
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How is the “intensity” of a fast radio burst measured?

I’ve read that Fast Radio Bursts are very “intense”, but how is intensity measured?
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Can I calculate frequency limits using bandwidth and center frequency?

I’m given the centre frequency and bandwidth of a radio transient. I need to determine the frequencies over which the transient occurred. I know there’s a relationship between the two, but I’ve ...
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28 views

What’s the difference between FoV and IFoV?

I read that radio telescopes have “huge fields of view (FoV)”, but are unable to precisely localized objects due to their “small instantaneous field of view (IFoV)”. Apparently, somehow the size of ...
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Why do high frequency radio telescope observations require precise localization?

Why do high frequency radio observations, particularly of transient phenomenon such as Fast Radio Burst and Pulsars, require increasingly precise localization with increasingly high frequency?
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42 views

Why is all the information contained in the sidebands?

Why is all the information contained only in the sidebands in AM? (And what is this supposed to mean? I read it off a textbook.) Also, why does an increase in bandwidth lead to an increase in quality ...
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1answer
38 views

Do terms like 'radiowave', 'ultraviolet', 'X-ray' mean the same thing in matter vs in vacuum/air?

I usually use terms like 'radiowave', 'microwave', 'X-ray', etc. to refer to ranges of electromagnetic (EM) frequencies ($f=2\pi/\omega$) or wavelengths ($\lambda = 2\pi/k$) in air or in a vacuum, ...
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Why X-ray and radio waves can penetrate walls but light can not? [duplicate]

Why can visible light, which lies in the middle between X-ray and radio waves in terms of frequency/energy, not penetrate walls?
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How to calculate Doppler Shift for multipaths from moving objects?

Let's say we have a radar where the transmitter and receiver are placed together, and form an angle theta with a target object moving with velocity ...
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Are X galaxies (PKS 2014-55) collisions?

Recent radio imaging by Meerkat of PKS2014-55 show an xshaped galaxy with a distinctive core and lobes. https://scholar.google.co.uk/scholar?hl=en&as_sdt=0%2C5&q=Pks+2014+meerkat&btnG=#d=...
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41 views

Long Range - High Frequency or Low Frequency

I have a confusion regarding which signal covers more distance - high frequency signal or low frequency signal? My understanding - high frequency signal has high energy. So, it has the energy to ...
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Does modulating a laser source change its color?

Hopefully you guys can solve this hypothetical for me. Suppose I have a laser which emits light at frequency $530\mathrm{THz}$ with a very narrow spectral width $1\mathrm{Hz}$. From signal theory, ...
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Simplified model of antenna polarization loss

I need to write a very simple model to estimate the $dB$ value of the polarization loss between two antennas (in realtime). Such antennas are common (yet identical) omnidirectional dipole antennas, ...
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Number of photons collected by a telescope [closed]

I’m trying to calculate how many photons of frequency $1420$ Mhz are collected by a telescope of area $100$ m$^2$ per second from the Andromeda Galaxy, which is 2 million light years away and has a ...
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1answer
32 views

How does computer identify routers differently? [closed]

Every router has its own name. What is physics that use in making router ideal one from another? Why we can't use same password to access all the routers? I know it sounds crazy but they all use 5GHz ...
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1answer
36 views

How to read a meter for radio and microwaves?

I am not clear on how to read this meter for radio waves and microwaves. The bottom band shows it measures from .01 to 1. First, I'm not sure what the units mean (mW/cm2). Radio waves are from 30KHz-...
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What piece of technology is able to record the exact phase of microwaves?

I read that in VLBI, the signals of microwaves are recorded and then later combined. A famous example of this is the Event Horizon Telescope which imaged the black hole. Presumably, the telescopes ...
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2answers
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How far can an x-ray travel through water?

I am studying x-ray's and how they interact with different mediums, but I am a bit confused on the distances an x-ray can travel through different mediums such as water. Let's take an x-ray with 3 ...
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Commercial Radio Bandwidths around the world

I'm a liberal arts person who has more than a passing interest in radio but it has taken years for this to dawn on me, so be kind if it is obvious. I was out of the US recently, and I saw a radio in ...
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1answer
53 views

How much can gravity affect light frequency?

I was wondering, maybe SETI cannot catch alien radio signals, because they don't monitor the right wavelengths. What if aliens live near a black hole or a denser region and radio signals coming from ...
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3answers
129 views

How gravity time dilation affect radio wave communication?

I'm not in any way an expert so sorry if my question is silly. So i was wondering about a hypothetical situation. I'm orbiting a black hole and I'm trying to contact via radio with someone outside the ...
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What is the relationship between average pulsar amplitude and the frequency?

Hi my question is pretty much in the title when im referring to frequency im referring to the frequency of the pulses. I have plotted a graph frequency vs average pulse amplitude but i don't ...
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1answer
36 views

Klystron output voltage, cavity physics

Can you please explain why almost nowhere do I see such a parameter as the output voltage from a klystron, it's easy to find the DC accelerating voltage of the beam and the electron bunch densities ...
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1answer
26 views

Wave Interference (Control Tower vs Mobile Phones)

I was curious about something regarding radio waves. When we're talking about differences of 200 MHz between waves, is there any way of any noticeable interference occurring? By noticeable I mean ...
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1answer
93 views

Can a lower frequency receiver antenna receive information from a higher frequency signal?

End goal: I wish to use a smartphone NFC transmitter (high-frequency RFID @ 13.56 MHz) to send data to a low-frequency RFID @ 120–150 kHz door reader to open the door. Illustrative example: HF ...
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2answers
46 views

Are radio waves naturally produced?

I am just wondering if radio waves are naturally produced. If so how?
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1answer
38 views

Irradiation at high frequency

I read this statement in Feynman Lecture on Physics (see here for more details): In low-frequency circuits the connection is made with wires, but this method doesn’t work very well at high ...
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Total thermal noise of a photodetector connected to a spectrum analyzer

I connected a photodetector to a spectrum analyzer (SA) and observed the signal (i.e. noise) on the SA when there is no light hitting the detector. I noticed that when I set a low spectral resolution ...
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82 views

How can cell phone towers transmit despite the rain?

I once read that waves of higher frequency (such as around 1 GHz range and higher) have difficulty passing through water (or other liquids/solids). Today, when I saw a cellphone tower, I wondered: "...
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26 views

Changing the refractive index of biological tissue using Radio Frequency (RF)

I have been looking into changing the refractive index of a specific medium initially using Ultrasound in a known location via a mechanical Doppler shift of the emitter (Mahan et al., 1998) which has ...
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30 views

Changing the refractive index of a specific medium using radio frequency (RF) waves

Using Ultrasound one can change the refractive index of a specific medium such as biological tissue, I was wondering if it is possible to change the refractive index of a medium such as biological ...
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40 views

Red shift of radio signals

If a radio signal is red-shifted does it still last the same amount of time? Knowing the signal wavelength is now longer but still is traveling at the speed of light one would assume the radio message ...
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131 views

How did German radio beams reach distant English cities during WWII? [closed]

During WWII, the Germans were using radio beacons (the "Knickebein" system) to guide their bombers into English territory. They set up two beacons, one in Kleve, a city in West Germany, and one at ...

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